Orientation device and method for coordinate generation employed thereby

ABSTRACT

A method for coordinate generation to be implemented using an orientation device includes the steps of: providing at least three reference marks on a target; aiming the orientation device at a target point on the target, and operating the orientation device such that the orientation device is able to capture an image of the target that contains the reference marks; assigning absolute coordinates to the reference marks in the image captured by the orientation device; and determining relative coordinates of the target point in a coordinate space of the target with reference to the absolute coordinates assigned to the reference marks. An orientation device that performs the method is also disclosed.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 11/392,089, filed on Mar. 28, 2006, which claimspriority to Taiwanese Application No. 094115044, filed May 10, 2005, thedisclosures of which are herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method for coordinate generation and to anorientation device that generates coordinates of target points using themethod.

2. Description of the Related Art

FIG. 1 illustrates a conventional light gun 8 for a video game system 9.The conventional light gun 8 includes an image sensor 82 and a timer 81.The video game system 9 further includes a display 91 and a gamecontroller 92. The display 91 includes a cathode-ray tube screen 910that presents images through interlace scanning. The game controller 92is installed with gaming software. The light gun 8 is connectedelectrically and transmits coordinate signals to the game controller 92,which then responds by controlling progress of the game, includingpresentation of images on the screen 910 of the display 91.

The conventional method for coordinate generation using theaforementioned conventional light gun 8 includes the following steps:

a) aiming the light gun 8 at a target point 911 on the screen 910 of thedisplay 91, and operating the light gun 8 such that the image sensor 82is able to capture an aimed part of the image presented on the screen910 of the display 91 and such that the timer 81 is able to determinethe scanning time at which the target point 911 is scanned withreference to the presentation of the image on the screen 910 of thedisplay 91; and

b) determining the coordinates of the target point 911 with reference tothe scanning time determined in step a).

The aforementioned method is disadvantageous since it is applicable onlyfor displays that employ interlace scanning technique.

SUMMARY OF THE INVENTION

Therefore, the object of the present invention is to provide a methodfor coordinate generation, which is applicable for targets that use anddo not use interlace scanning.

Another object of the present invention is to provide an orientationdevice which generates coordinates of target points and which issuitable for targets that use and do not use interlace scanning.

According to one aspect of the present invention, a method forcoordinate generation is implemented using an orientation device that isprovided with a sensor, and comprises the steps of:

A) providing at least three reference marks on a target;

B) aiming the orientation device at a target point on the target, andoperating the orientation device such that the sensor is able to capturean image of the target that contains the reference marks;

C) assigning absolute coordinates to the reference marks in the imagecaptured in step B); and

D) determining relative coordinates of the target point in a coordinatespace of the target with reference to the absolute coordinates of thereference marks assigned in step C).

According to another aspect of the present invention, a system comprisesa target, at least three reference marks, and an orientation device. Thetarget defines a coordinate space. The reference marks are provided onthe target. The orientation device defines a coordinate space correlatedwith the coordinate space of the target, and includes a sensor and aprocessor. The sensor is able to capture an image of the target thatcontains the reference marks when the orientation device is operatedwhile aiming at a target point on the target. The processor is coupledto the sensor, and is operable so as to compute absolute coordinates ofthe reference marks in the image captured by the sensor and so as todetermine relative coordinates of the target point in the coordinatespace of the target with reference to the absolute coordinates of thereference marks.

According to yet another aspect of the present invention, there isprovided an orientation device for a system, which includes a targetprovided with at least three reference marks. The orientation devicedefines a coordinate space correlated with a coordinate space of thetarget, and comprises a sensor and a processor. The sensor is adapted tocapture an image of the target that contains the reference marks whenthe orientation device is operated while aiming at a target point on thetarget. The processor is coupled to the sensor, and is operable so as tocompute absolute coordinates of the reference marks in the imagecaptured by the sensor and so as to determine relative coordinates ofthe target point in the coordinate space of the target with reference tothe absolute coordinates of the reference marks.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will becomeapparent in the following detailed description of the preferredembodiments with reference to the accompanying drawings, of which:

FIG. 1 is a perspective view of a conventional video game system;

FIG. 2 is a schematic view of a system that incorporates the preferredembodiment of an orientation device according to the present invention;

FIG. 3 is a schematic block diagram of the preferred embodiment;

FIGS. 4A and 4B are flowcharts to illustrate the first preferredembodiment of a method for coordinate generation using an orientationdevice according to the present invention;

FIG. 5 illustrates a target point aimed by the orientation device;

FIG. 6 illustrates an axis correction value determined by theorientation device;

FIGS. 7A and 7B are flowcharts to illustrate the second preferredembodiment of a method for coordinate generation using an orientationdevice according to the present invention;

FIG. 8 illustrates a transformation matrix (H_(inner)) obtained byperforming the second preferred embodiment of the method;

FIG. 9 illustrates a transformation matrix (H_(any)) obtained byperforming the second preferred embodiment of the method;

FIGS. 10A to 10C are flowcharts to illustrate the third preferredembodiment of a method for coordinate generation using an orientationdevice according to the present invention;

FIG. 11 is a schematic view to illustrate the orientation device aimedat a target and rotated about an image-capturing axis thereof; and

FIG. 12 is a schematic view to illustrate mapping of coordinates ofreference marks into vectors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 2 and 3, the preferred embodiment of an orientationdevice 3 of a system 100 according to this invention is shown to includea controller module 32, a light filter 33, a lens 34, and a casing 31.

The system 100 further includes a target 11, four reference marks 111,112, 113, 114, and a game controller 12.

The target 11, in this embodiment, is a display that includes agenerally rectangular screen 110, which defines a coordinate space.Preferably, the display 11 may be a liquid crystal display (LCD), aplasma display panel (PDP) display, a cathode-ray tube (CRT) display, ora projector display. In an alternative embodiment, the target 11 may bea wall, a projector screen, or a ceiling.

The reference marks 111, 112, 113, 114 are provided on the screen 110 ofthe display 11. In this embodiment, each of the reference marks 111,112, 113, 114 is a light source. Preferably, each of the reference marks111, 112, 113, 114 is a light-emitting diode. In an alternativeembodiment, each of the reference marks 111, 112, 113, 114 may be areflector or a colored pattern.

Although the system 100 of this invention is exemplified using four ofthe reference marks 111, 112, 113, 114, it should be noted that thenumber of reference marks 111, 112, 113, 114 may be reduced to three.

The game controller 12 is installed with gaming software in a mannerwell known in the art, is coupled to the screen 110 of the display 11and the orientation device 3, and includes a communications interface121. In this embodiment, the communications interface 121 of the gamecontroller 12 is a serial communications interface. In an alternativeembodiment, the communications interface 121 of the game controller 12is a parallel communications interface.

The orientation device 3 of this embodiment is a light gun that definesa coordinate space. In this embodiment, the orientation device 3 isoperable so as to generate coordinates of a target point aimed therebyon the screen 110 of the display 11, in a manner that will be describedhereinafter.

The controller module 32 of the orientation device 3 includes a sensor321, a processor 322, a memory 324, and a communications interface 323.

The sensor 321 of the controller module 32 of the orientation device 3is operable so as to capture an image of the screen 110 of the display11 that contains the reference marks 111, 112, 113, 114 and so as toconvert the captured image into a digitized image. In this embodiment,the sensor may be a complementary metal-oxide-semiconductor (CMOS)device or a charged-coupled device (CCD).

The processor 322 of the controller module 32 of the orientation device3 is coupled to the sensor 321 of the controller module 32 of theorientation device 3, and is operable so as to receive and process thedigitized image accordingly.

The memory 324 of the controller module 32 of the orientation device 3is coupled to the processor 322 of the controller module 32 of theorientation device 3, and serves to temporarily store the digitizedimage processed by the processor 322.

The communications interface 323 of the controller module 32 of theorientation device 3 is coupled to the processor 322, and is connectedelectrically to the communications interface 121 of the game controller12 for transmitting signals between the orientation device 3 and thegame controller 12, in a manner well known in the art. In thisembodiment, the communications interface 323 of the controller module 32of the orientation device 3 is a serial communications interface. In analternative embodiment, the communications interface 323 of thecontroller module 32 of the orientation device 3 is a parallelcommunications interface.

The light filter 33 of the orientation device 3 is disposed in front ofthe sensor 321 of the controller module 32 of the orientation device 3,and serves to filter undesired light spectrum.

The lens 34 of the orientation device 3 is disposed between the lightfilter 33 and the sensor 321.

The casing 31 of the orientation device 3 is in the shape of a gun, andhouses the light filter 33, the lens 34, and the controller module 32.

The first preferred embodiment of a method for coordinate generation tobe implemented using the orientation device 3 of the system 100according to this invention is described with further reference to FIG.4A.

In step 41, as illustrated in FIG. 5, each of the reference marks 111,112, 113, 114 is provided on a respective one of the corners of thescreen 110 of the display 11. That is, the coordinates of each of thereference marks 111, 112, 113, 114 are identical to those of the cornersof the screen 110 of the display 11.

In step 42, the orientation device 3 is aimed at one of the referencemarks 111, 112, 113, 114, such as the reference mark 111, on the screen110 of the display 11.

In step 43, the orientation device 3 is operated such that the sensor321 of the controller module 32 of the orientation device 3 is able tocapture an image of the screen 110 of the display 11 that contains thereference mark 111 aimed in step 42.

In step 44, from the image captured in step 43, the processor 322 of thecontroller module 32 of the orientation device 3 correlates thecoordinate space of the orientation device 3 with the coordinate spaceof the screen 110 of the display 11.

It is noted that, in this step, the processor 322 of the controllermodule 32 of the orientation device 3 determines an axis correctionvalue (X_(ref)) associated with mapping of the reference mark 111 ontothe coordinate space of the orientation device 3, as illustrated in FIG.6. In this embodiment, the axis correction value (X_(ref)) refers to anelevation angle formed by the orientation device 3 with an axis 6 of thereference mark 111 on the screen 110 of the display 11.

In step 45, the orientation device 3 is aimed at a target point(P_(any)) on the screen 110 of the display 11.

In step 46, the orientation device 3 is operated such that the sensor321 of the controller module 32 of the orientation device 3 is able tocapture an image of the screen 110 of the display 11 that contains thereference marks 111, 112, 113, 114.

In step 47, the processor 322 of the controller module 32 of theorientation device 3 determines the relative coordinates of the targetpoint (P_(any)) with reference to the coordinate space relationestablished in step 44 and the image captured in step 46. Thereafter,the flow goes back to step 45.

In this embodiment, with further reference to FIG. 4B, step 47 includesthe sub-steps of:

sub-step 471: determining coordinates of the reference marks 111, 112,113, 114 in the image captured in step 46;

sub-step 472: performing planar projective transformation calculationsupon the coordinates of the reference marks 111, 112, 113, 114determined in sub-step 471 to obtain a transformation matrix (H_(any));

sub-step 473: correcting an image capturing axis 6′ (see FIG. 6) of thesensor 321 of the controller module 32 of the orientation device 3 withreference to the transformation matrix (H_(any)) obtained in sub-step472 and the axis correction value (X_(ref)) obtained in step 44; and

sub-step 474: determining the relative coordinates of the target point(P_(any)) with reference to the corrected image capturing axis 6′.

It is noted that steps 41 to 44 are performed only to calibrate theorientation device 3. Once calibrated, steps 41 to 44 are skipped.

The second preferred embodiment of a method for coordinate generation tobe implemented using the orientation device 3 of the system 100according to this invention will now be described with further referenceto FIG. 7A.

In step 71, as illustrated in FIG. 8, each of the reference marks 111,112, 113, 114 is provided adjacent to a respective one of the corners(A, B, C, D) of the screen 110 of the display 11. That is, thecoordinates of each of the reference marks 111, 112, 113, 114 aredistinct from those of the respective adjacent corner (A, B, C, D) ofthe screen 110 of the display 11.

In step 72, the orientation device 3 is aimed at one of the referencemarks 111, 112, 113, 114, such as the reference mark 111, on the screen110 of the display 11.

In step 73, the orientation device 3 is operated such that the sensor321 of the controller module 32 of the orientation device 3 is able tocapture an image of the screen 110 of the display 11 that contains thereference mark 111 aimed in step 72.

In step 74, from the image captured in step 73, the processor 322 of thecontroller module 32 of the orientation device 3 correlates thecoordinate space of the orientation device 3 with the coordinate spaceof the screen 110 of the display 11.

It is noted that, in this step, the processor 322 of the controllermodule 32 of the orientation device 3 determines an axis correctionvalue (X_(ref)) associated with mapping of the reference mark 111 ontothe coordinate space of the orientation device 3, as illustrated in FIG.6.

In step 75, the orientation device 3 is aimed at an arbitrary point(P_(inner)) on the screen 110 of the display 11.

In step 76, the orientation device 3 is operated such that the sensor321 of the controller module 32 of the orientation device 3 is able tocapture an image of the screen 110 of the display 11 that contains thereference marks 111, 112, 113, 114.

In step 77, the orientation device 3 is aimed at the upper left corner(A) of the screen 110 of the display 11.

In step 78, the orientation device 3 is operated such that the sensor321 of the controller module 32 of the orientation device 3 is able tocapture an image of the screen 110 of the display 11 that contains thereference marks 111, 112, 113, 114.

In step 79, the orientation device 3 is aimed at the upper right corner(B) of the screen 110 of the display 11.

In step 80, the orientation device 3 is operated such that the sensor321 of the controller module 32 of the orientation device 3 is able tocapture an image of the screen 110 of the display 11 that contains thereference marks 111, 112, 113, 114.

In step 81, the orientation device 3 is aimed at the lower right corner(C) of the screen 110 of the display 11.

In step 82, the orientation device 3 is operated such that the sensor321 of the controller module 32 of the orientation device 3 is able tocapture an image of the screen 110 of the display 11 that contains thereference marks 111, 112, 113, 114.

In step 83, the orientation device 3 is aimed at the lower left corner(D) of the screen 110 of the display 11.

In step 84, the orientation device 3 is operated such that the sensor321 of the controller module 32 of the orientation device 3 is able tocapture an image of the screen 110 of the display 11 that contains thereference marks 111, 112, 113, 114.

In step 85, as illustrated in FIG. 9, the orientation device 3 is aimedat a target point (P_(any)) on the screen 110 of the display 11.

In step 86, the orientation device 3 is operated such that the sensor321 of the controller module 32 of the orientation device 3 is able tocapture an image of the screen 110 of the display 11 that contains thereference marks 111, 112, 113, 114.

In step 87, the processor 322 of the controller module 32 of theorientation device 3 determines the relative coordinates of the targetpoint (P_(any)) with reference to the coordinate space relationestablished in step 74, and the images captured in steps 76, 78, 80, 82,84 and 86. Thereafter, the flow goes back to step 85.

In this embodiment, with further reference to FIG. 7B, step 87 includesthe sub-steps of:

sub-step 871: determining coordinates of the reference marks 111, 112,113, 114 in the image captured in step 76;

sub-step 872: performing planar projective transformation calculationsupon the coordinates of the reference marks determined in sub-step 871to obtain a transformation matrix (H_(inner)), as illustrated in FIG. 8;

sub-step 873: determining coordinates of the reference marks 111, 112,113, 114 in the images captured in steps 78, 80, 82, and 84;

sub-step 874: performing planar projective transformation calculationsupon the coordinates of the reference marks 111, 112, 113, 114determined in sub-step 873 to obtain transformation matrices (H_(a),H_(b), H_(c), H_(d));

sub-step 875: determining coordinates of the reference marks 111, 112,113, 114 in the image captured in step 86;

sub-step 876: performing planar projective transformation calculationsupon the coordinates of the reference marks 111, 112, 113, 114determined in sub-step 875 to obtain a transformation matrix (H_(any))as illustrated in FIG. 9;

sub-step 877: correcting an image-capturing axis 6′ of the sensor 321 ofthe controller module 32 of the orientation device 3 with reference tothe transformation matrix (H_(inner)) obtained in sub-step 872, thetransformation matrices (H_(a), H_(b), H_(c), H_(d)) obtained insub-step 874, the transformation matrix (H_(any)) obtained in sub-step876, and the axis correction value (X_(ref)) obtained in step 74; and

sub-step 878: determining the relative coordinates of the target point(P_(any)) with reference to the corrected image capturing axis 6′.

It is noted that steps 71 to 84 are performed only to calibrate theorientation device 3. Once calibrated, steps 71 to 84 are skipped.

The third preferred embodiment of a method for coordinate generation tobe implemented using the orientation device 3 of the system 100according to this invention will now be described with further referenceto FIG. 10A.

In step 101, as illustrated in FIG. 11, each of the reference marks 111,112, 113, 114 is provided adjacent to a respective one of the corners(A, B, C, D) of the screen 110 of the display 11. That is, thecoordinates of each of the reference marks 111, 112, 113, 114 aredistinct from those of the respective adjacent corner (A, B, C, D) ofthe screen 110 of the display 11.

In step 102, the orientation device 3 is aimed at one of the referencemarks 111, 112, 113, 114, such as the reference mark 111, on the screen110 of the display 11.

In step 103, the orientation device 3 is operated such that the sensor321 of the controller module 32 of the orientation device 3 is able tocapture an image of the screen 110 of the display 11 that contains thereference mark 111 aimed in step 102.

In step 104, from the image captured in step 103, the processor 322 ofthe controller module 32 of the orientation device 3 correlates thecoordinate space of the orientation device 3 with the coordinate spaceof the screen 110 of the display 11.

It is noted that, in this step, the processor 322 of the controllermodule 32 of the orientation device 3 determines an axis correctionvalue (X_(ref)) associated with mapping of the initial point 111 ontothe coordinate space of the orientation device 3, as illustrated in FIG.6.

In step 105, the orientation device 3 is aimed at an arbitrary point(P_(inner)) on the screen 110 of the display 11.

In step 106, the orientation device 3 is operated such that the sensor321 of the controller module 32 of the orientation device 3 is able tocapture an image of the screen 110 of the display 11 that contains thereference marks 111, 112, 113, 114.

In step 107, the orientation device 3 is aimed at the upper left corner(A) of the screen 110 of the display 11.

In step 108, the orientation device 3 is operated such that the sensor321 of the controller module 32 of the orientation device 3 is able tocapture an image of the screen 110 of the display 11 that contains thereference marks 111, 112, 113, 114.

In step 109, the orientation device 3 is aimed at the upper right corner(B) of the screen 110 of the display 11.

In step 110, the orientation device 3 is operated such that the sensor321 of the controller module 32 of the orientation device 3 is able tocapture an image of the screen 110 of the display 11 that contains thereference marks 111, 112, 113, 114.

In step 111, the orientation device 3 is aimed at the lower right corner(C) of the screen 110 of the display 11.

In step 112, the orientation device 3 is operated such that the sensor321 of the controller module 32 of the orientation device 3 is able tocapture an image of the screen 110 of the display 11 that contains thereference marks 111, 112, 113, 114.

In step 113, the orientation device 3 is aimed at the lower left corner(D) of the screen 110 of the display 11.

In step 114, the orientation device 3 is operated such that the sensor321 of the controller module 32 of the orientation device 3 is able tocapture an image of the screen 110 of the display 11 that contains thereference marks 111, 112, 113, 114.

In step 115, as illustrated in FIG. 12, the orientation device 3 isaimed at a target point (P_(any)) on the screen 110 of the display 11.

In step 116, the orientation device 3 is operated such that the sensor321 of the controller module 32 of the orientation device 3 is able tocapture an image of the screen 110 of the display 11 that contains thereference marks 111, 112, 113, 114.

In step 117, the reference marks 111, 112, 113, 114 are assigned withabsolute coordinates in the image captured in step 116.

In this embodiment, with further reference to FIG. 10B, step 117includes the sub-steps of:

sub-step 1171: computing coordinates of the reference marks 111, 112,113, 114 in the image captured in step 116 to obtain vectorcombinations;

sub-step 1172: finding a pair of most parallel vectors, such as (EF) and(GH), from the vector combinations obtained in sub-step 1171;

It is noted that the pair of most parallel vectors has a largestabsolute value of vector inner product compared to those of the othervector pairs (or vector combinations).

sub-step 1173: forming a first mark group from one of the vectors (EF),i.e., the shorter vector, found in sub-step 1172, and a second markgroup from the other of the vectors (GH), i.e., the longer vector, foundin sub-step 1172;

sub-step 1174: finding a pair of the vectors, such as (HF) and (HE), avertex (H) of which is found in the second mark group, and endpoints (E,F) of which are found in the first mark group;

sub-step 1175: obtaining the absolute coordinates of the endpoints (E,F) in the first mark group based on a vector product of the vectors (HF,HE) found in sub-step 1174;

It is noted that, according to the right-hand rule, if the cross productof the vectors (HF, HE), i.e., (HF)×(HE), is greater than zero, or ifthe cross product of the vectors (HE, HF), i.e., (HE)×(HF), is less thanzero, the endpoints (E, F) respectively correspond to the referencemarks 111, 112.

sub-step 1176: determining a pair of the vectors, such as (EG) and (EH),a vertex (E) of which is found in the first mark group, and endpoints(G, H) of which are found in the second mark group; and

sub-step 1177: obtaining the absolute coordinates of the endpoints (G,H) in the second mark group based on a vector product of the vectors(EG, EH) found in sub-step 1176.

It is noted that, according to the right-hand rule, if the cross productof the vectors (EG, EH), i.e., (EG)×(EH), is greater than zero, or ifthe cross product of the vectors (EH, EG), i.e., (EH)×(EG) is less thanzero, the endpoints (G, H) respectively correspond to the referencemarks 114, 113.

In step 118, the processor 322 of the controller module 32 of theorientation device 3 determines the relative coordinates of the targetpoint (P_(any)) with reference to the coordinate space relationestablished in step 104, the images captured in steps 106, 108, 110,112, 114 and 116, and the absolute coordinates of the reference marks111, 112, 113, 114 assigned in step 117. Thereafter, the flow goes backto step 115.

In this embodiment, with further reference to FIG. 10C, step 118includes the sub-steps of:

sub-step 1181: determining coordinates of the reference marks 111, 112,113, 114 in the image captured in step 106;

sub-step 1182: performing planar projective transformation calculationsupon the coordinates of the reference marks 111, 112, 113, 114determined in sub-step 1181 to obtain a transformation matrix(H_(inner));

sub-step 1183: determining coordinates of the reference marks 111, 112,113, 114 in the images captured in steps 108, 110, 112, and 114;

sub-step 1184: performing planar projective transformation calculationsupon the coordinates of the reference marks 111, 112, 113, 114determined in sub-step 1183 to obtain transformation matrices (H_(a),H_(b), H_(c), H_(d));

sub-step 1185: performing planar projective transformation calculationsupon the absolute coordinates of the reference marks assigned in step117 to obtain a transformation matrix (H_(any));

sub-step 1186: correcting an image-capturing axis 6′ of the sensor 321of the controller module 32 of the orientation device 3 with referenceto the transformation matrix (H_(inner)) obtained in sub-step 1182, thetransformation matrices (H_(a), H_(b), H_(c), H_(d)) obtained insub-step 1184, the transformation matrix (H_(any)) obtained in sub-step1185, and the axis correction value (X_(ref)) obtained in step 104; and

sub-step 1187: determining the relative coordinates of the target point(P_(any)) with reference to the corrected image capturing axis 6′.

It is noted that steps 101 to 114 are performed only to calibrate theorientation device 3. Once calibrated, steps 101 to 114 are skipped.Furthermore, unlike in the previous embodiments, in this embodiment, therelative coordinates of the target point (P_(any)) are determined withreference to the absolute coordinates of the reference marks 111, 112,113, 114 assigned in step 117. As such, the relative coordinates of thetarget point (P_(any)) can be accurately determined in step 118 evenwhen the orientation device 3 is rotated about the image-capturing axis6′ in step 115.

It has thus been shown that, in the method and orientation device 3 ofthis invention, relative coordinates of target points are generatedwithout referring to scanning information of images presented on thedisplays. The present invention is thus applicable to a wide variety oftargets, including those displays that do not use interlace scanning.

While the present invention has been described in connection with whatare considered the most practical and preferred embodiments, it isunderstood that this invention is not limited to the disclosedembodiments but is intended to cover various arrangements includedwithin the spirit and scope of the broadest interpretation so as toencompass all such modifications and equivalent arrangements.

1. A method for coordinate generation to be implemented using anorientation device that is provided with a sensor, said methodcomprising the steps of: A) providing at least four reference marks on atarget; B) aiming the orientation device at a target point on thetarget, and operating the orientation device such that the sensor isable to capture an image of the target that contains the referencemarks; C1) computing coordinates of the reference marks in the imagecaptured in step B) to obtain vector combinations; C2) finding a pair ofmost parallel vectors from the vector combinations, and obtainingabsolute coordinates of the reference marks projected onto thecoordinate space of the target according to the pair of most parallelvectors; and D) determining relative coordinates of the target point ina coordinate space of the target with reference to the absolutecoordinates of the reference marks assigned in step C2); E) aiming theorientation device at an arbitrary point on the target; and F) operatingthe orientation device such that the sensor is able to capture an imageof the target that contains the reference marks; wherein step D)includes the sub-steps of: D1) determining coordinates of the referencemarks from the image captured in step F); D2) performing projectivetransformation calculations upon the coordinates of the reference marksdetermined in sub-step Dl) to obtain a transformation matrix; D3)correcting an image-capturing axis of the sensor of the orientationdevice with reference to the transformation matrix obtained in sub-stepD2) and an established coordinate space relation between the target andthe orientation device; and D4) determining the relative coordinates ofthe target point with reference to the corrected image-capturing axis.2. The method as claimed in claim 1, further comprising the steps of: G)aiming the orientation device at one of the reference marks; H)operating the orientation device such that the sensor is able to capturean image of the target that contains the reference mark aimed in stepG); I) determining the coordinates of the reference mark aimed in stepG) from the image captured in step H); and J) correlating a coordinatespace of the orientation device with a coordinate space of the target tothereby establish the coordinate space relation.
 3. A method forcoordinate generation to be implemented using an orientation device thatis provided with a sensor, said method comprising the steps of: A)providing at least four reference marks on a target; B) aiming theorientation device at a target point on the target, and operating theorientation device such that the sensor is able to capture an image ofthe target that contains the reference marks; C1) computing coordinatesof the reference marks in the image captured in step B) to obtain vectorcombinations; C2) finding a pair of most parallel vectors from thevector combinations, and obtaining absolute coordinates of the referencemarks projected onto the coordinate space of the target according to thepair of most parallel vectors; and D) determining relative coordinatesof the target point in a coordinate space of the target with referenceto the absolute coordinates of the reference marks assigned in step,C2); E) aiming the orientation device at one corner of the target, andoperating the orientation device such that the sensor is able to capturean image of the target that contains the reference marks; wherein stepD) includes the sub-steps of: D1) determining coordinates of thereference marks from the image captured in step E); D2) performingprojective transformation calculations upon the coordinates of thereference marks determined in sub-step D1) to obtain a transformationmatrix; D3) correcting an image-capturing axis of the sensor of theorientation device with reference to the transformation matrix obtainedin sub-step D2); and D4) determining the relative coordinates of thetarget point with reference to the corrected image-capturing axis.